Auditory Tracts Flashcards
Where are cell bodies of the auditory pathways found?
Spiral ganglion
Where do the nerves of the auditory pathways enter the brainstem?
Pontomedullary junction
Where do the nerves of the auditory pathways synapse?
Cochlear nuclei
What are the different cochlear nuclei?
Dorsal cochlear and ventral cochlear (subdivided into anterior/posterior divisions)
What information do monaural tracts transmit? Where does this information go?
Information about sounds at a single ear; routed to contralateral side
What information do binaural tracts transmit? Where does this information go?
Information about differences between sounds at both ears; handled by central pathways that receive, compare, and transmit this input
What is conduction deafness?
Deficit related to an obstructed, or altered, transformation of sound to the tympanic membrane or through ossicle chain
What is sensorineural (nerve) deafness?
Results from damage to the cochlea, the cochlear part of CN VIII or to the cochlear nuclei
What is central deafness?
Damage to the central pathways
What is the origin of blood supply to the cochlea and auditory nuclei of the pons and medulla?
Basilar artery
What supplies the inner ear and the cochlear nuclei?
Internal auditory (labyrinthine) artery, usually a branch of AICA
What will occlusion of the AICA result in?
Monaural hearing loss; may also damage the emerging fibers of the facial nerve and the pontine gaze center, resulting in monaural deafness combined with ipsilateral facial paralysis and an inability to look toward the side of the lesion
What supplies the superior olivary complex and lateral lemniscus?
Short circumferential branches of the basilar
What supplies the inferior coliculus?
Superior cerebellar and quadrigeminal arteries
What supplies the medial geniculate bodies?
Thalamogeniculate arteries
What supplies the primary auditory and association cortices?
M2 segment of the middle cerebral artery
What is the function of Wernicke’s area?
Comprehension of spoken language
What is the function of Broca’s area?
Instruction for language output, planning movements to produce speech, and providing grammatical function of words
What is the dominant hemisphere?
Left hemisphere in 94% of adults
In the right hemisphere, what is the function of the area analogous to Wernicke’s area?
Interpreting nonverbal signals from other people
In the right hemisphere, what is the function of the area analogous to Broca’s area?
Instructions for producing non-verbal communication including emotional gestures and intonation of speech
What is agnosia? What is auditory agnosia?
Agnosia: inability to identify an object despite being able to perceive it
Auditory Agnosia: inability to describe a sound that has been heard
Lesion is unimodal sensory association cortex bilaterally
What does a lesion in Wernicke’s area cause?
Wernicke’s aphasia (receptive or fluent); defect of the comprehension of language, but expression is fine
Also unable to understand what is said to them, unable to read (alexia), unable to write comprehensible language (agraphia), or display fluent paraphasic speech
What does a lesion in Broca’s area cause?
Broca’s aphasia (expressive aphasia or non-fluent aphasia); loss of the ability to speak fluently, but can understand spoken and written language
Severe: results in inability to speak (mutism)
Minor: limited speech, short habitual phrases (hi, yes, no); speech is slow, labored, poor enunciation; nonessential words are omitted
What is a global lesion?
Type of non-fluent aphasia; lesion of lateral sulcus; receptive and expressive deficits, reading and writing impaired
What is conduction aphasia?
Type of fluent aphasia; lesion of supramarginal gyrus and arcuate fasciculus; can’t repeat, intact fluency, good comprehension, speech interrupted by word-finding difficulties; reading intact, writing impaired
What is a transcortical motor lesion?
Nonfluent type; grammar preserved, comprehension is normal, naming and repetition is preserved; occurs at ACA-MCA border zone
What is a transcortical sensory lesion?
Fluent type; grammar is preserved, comprehension and naming is impaired, repetition is preserved; occurs at MCA-PCA border zone
